This invention relates to an uninterruptible power supply device of computers or communication apparatuses, connecting to a circuit for degradation judgment for a storage battery built therein.
Supplying a current from an alternating power to various communication apparatuses and so on, the uninterruptible power supply device is inserted between the alternating power and such a communication apparatus in order to prevent the power from stopping by its unexpected failure or an interception of a breaker and damaging the apparatus or interrupting work.
There are two types of a normal converter power supply system and a normal supply system from a commercial power roughly dividing such uninterruptible power supply devices. The former is equipped with a rectification circuit, a storage battery and a converter. It normally carries out floating charge to the storage battery with a direct current obtained from the rectification circuit and supplying an alternating current converting from the direct current by the converter to the load apparatus. In the latter, the alternating current is directly supplied from an alternating power to the load apparatus. On the other hand, the storage batter is carried out such floating charge with a direct current of an alternating-direct current conversion from the power.
If any type of the uninterruptible power supply devices stop to be supplied power at power failure etc., the storage battery will discharge and a direct-alternating current conversion of the discharge current will be carried out. And as long as the discharge of the storage battery continues, power is supplied and the load apparatus continues to drive without an intermission. If the power failure and so on stops in the meantime, it will return to the usual power supply state.
The storage battery degrades by over discharge of itself or drives of itself for a long range time. If the storage battery of the uninterruptible power supply device has degraded, discharge will not continue for a long time and the power source will not return in time, or if the degradation is remarkable, the discharge voltage is insufficient to drive the load apparatus.
Therefore, an uninterruptible power supply device attaches a circuit for judging the degradation of the storage battery. It is most generally known such a circuit judges by comparing a curve of the instant discharge current of the storage battery and a discharge curve of a normal storage battery i.e. reference curve thereof. It is also known that an impedance of such a storage battery is measured to judge the degradation. Japanese Patent Provisional Publication No. 2000-50525 discloses a method for judging the degradation by observing discharge progress of the storage battery when reducing a supplying voltage to the load from the power converter to make the storage battery discharge.
However, these prior judgment methods take a long time to make the storage battery discharge until the curve of the discharge current is obtained enough. A reference curve according to a kind of a storage battery or/and a discharging rate thereof is required and that a memory for the reference curve is required. A setup thus becomes complicated. Moreover, judging promotes the degradation of the storage battery since an unusual burden is applied thereto. Actually, when the storage battery has degraded, the discharge may stop during the judgment, and an original function may be unable to be achieved as an uninterruptible power source.